Semiconductor memory device with shift redundancy circuits

ABSTRACT

A semiconductor memory device including a shift redundancy circuit with two buffer chains, two fuses connected to the shift redundancy circuit, a plurality of fuse cut-out detecting circuits for detecting cut-out status of the fuses, and two spare cell control circuits for controlling two spare memory cell rows, wherein word line control signals for controlling corresponding word lines connected to memory cells in a memory cell array are shifted upward and downward to control respective next word lines, thereby replacing two defective memory cell rows with the two spare memory cell rows.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 10/631,766,filed on Aug. 1, 2003 which claims priority under 35 U.S.C. § 119 ofKorean Patent Application 2002-46919 filed on Aug. 8, 2002; the entirecontents of both of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor memory device, and moreparticularly to a semiconductor memory device having shift redundancycircuits.

2. Description of the Related Art

Semiconductor memory devices may have defective memory cell rows thatcan hinder the operation of the memory device and hence are undesirable.In the case where a defective memory cell row is present in a memorycell array, instead of controlling its corresponding word line, a wordline control signal controls the respective next word line by beingsequentially shifted in a direction, downward or upward. In conventionalsemiconductor memory devices, the word line selections are shifted inonly one direction, upward or downward. Accordingly, in the case that asemiconductor memory device has two or more defective memory cell rowsin a memory cell array, such semiconductor memory device may not berepairable. That is, conventional semiconductor memory devices aredesigned so that only one defective memory cell row can be repaired.

FIG. 1 is a schematic block diagram of a conventional semiconductormemory device. Referring to FIG. 1, a conventional semiconductor memorydevice includes a row decoder 10, a fuse circuit block 20, a shiftredundancy circuit block 30, a fuse cut-out detecting circuit block 40,and a memory cell array 50.

The fuse circuit block 20 includes fuses f1 to fn which are seriallyconnected. The semiconductor memory device shown in FIG. 1 has one sparememory cell row. Word lines R1 to Rn connected to memory cells areshifted through corresponding transmission gates T1 a to Tna, T1 b toTnb. NMOS transistors Q1, Q2 a to Qna, Q2 b to Qnb connected to thecorresponding word lines R1 to Rn are used to disable the correspondingword lines R1 to Rn having at least one defective memory cell. An outputof the row decoder 10 is used as an input of a next memory cell rowwhich is near the corresponding memory cell row in the downwarddirection as well as an input of the corresponding memory cell row.

Each fuse f1 to fn has an end connected to a power supply voltage Vccand the other end connected to a ground voltage Vss. Since the fuses f1to fn are connected between the power supply voltage Vcc and the groundvoltage Vss, in the case that the memory cell array 50 does not have adefective memory cell row, the power supply voltage may be supplied tothe shift redundancy circuit block 30. Accordingly, the transmissiongates Tia (“i” is an integer) are turned on and the transmission gatesTib are turned off, so that the word lines R1 to Rn are connected tocorresponding memory cell rows in the memory cell array 50. That is, theword lines R1 to Rn are not shifted. Further, the last transmission gateTnb is turned off and the NMOS transistor Qn+1 connected to a spare wordline Rn+1 is turned on, so that the spare word line Rn+1 is disabled.

On the other hand, in the case that the memory cell array 50 has adefective memory cell row, the fuse corresponding to the defectivememory cell row is cut out and shift redundancy circuits in the shiftredundancy circuit block 30 are divided into two groups, a groupreceiving power supply voltage Vcc and a group receiving ground voltageVss.

The shift redundancy circuits in the group receiving power supplyvoltage Vcc act as normal shift redundancy circuits, so that the wordlines are not shifted. However, for the shift redundancy circuits in thegroup receiving ground voltage Vss, since the fuses are connected to theground voltage Vss, the transmission gate Tia is turned off and thetransmission gate Tib is turned on, so that the word lines are shifted.That is, assuming that there is a defective memory cell row, atransmission gate corresponding to the defective memory cell row isturned off, and a word line corresponding to the defective memory cellrow is disabled by NMOS transistors Qia, Qib, so that the word line isshifted down by one row. As a result, a spare memory cell row positionedat the lowermost portion of the memory cell array 50 is used.

However, the conventional semiconductor memory device as described aboveis disadvantageous in that repairing efficiency is low when thesemiconductor memory device has two or more spare memory cell rows. Thatis, since the word lines in the conventional semiconductor memory deviceare shifted in only one direction, upward or downward, even if two sparememory cell rows are provided to the semiconductor memory device, twodefective memory cell rows can not be repaired when the two defectiverows are presented in the same memory cell array block. Further, theconventional semiconductor memory device as shown in FIG. 1 isdisadvantageous in that there is a leakage current caused by fuseresistance, and further the semiconductor memory device may malfunctiondue to the voltage drop when the series of fuses is long and theresistance of each fuse is high.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provides a semiconductormemory device with shift redundancy circuits capable of repairing two ormore defective memory cell rows in a memory cell array block. Exemplaryembodiments of the present invention provide a method for locating thespare memory cell rows when one or more spare memory cell rows exist. Anexemplary embodiment of the present invention, is directed to asemiconductor memory device comprising at least two shift redundancycircuits with at least two buffer chains, at least two fuses connectedto each of the shift redundancy circuits, at least two fuse cut-outdetecting circuits connected to each of the shift redundancy circuitsfor detecting cut-out status of the fuses, and at least two spare cellcontrol circuits for controlling at least two spare memory cell rows,wherein word line control signals for controlling corresponding wordlines connected to memory cells in a memory cell array are shiftedupward or downward, thereby replacing at least two defective memory cellrows with the at least two spare memory cell rows.

Another exemplary embodiment of the present invention provides asemiconductor memory device with first to n-th shift redundancycircuits, including: a row decoder for generating a plurality of wordline control signals; a plurality of shift redundancy circuits forreceiving at least three word line control signals of the word linecontrol signals, and transmitting at least one word line control signalamong the received three word line control signals; a plurality of upperfuses and a plurality of lower fuses, each being connected between apower supply voltage and a corresponding shift redundancy circuit; aplurality of upper and lower fuse cut-out detecting circuits reset by areset signal, each of which receives an output of either a correspondingupper fuse or a corresponding lower fuse, and enables or disablesrespective outputs of the corresponding shift redundancy circuits; afirst spare cell control circuit for receiving a first word line controlsignal and a third output signal of the first shift redundancy circuit,and generating a first spare cell control signal; a second spare cellcontrol circuit for receiving an n-th word line control signal and asecond output signal of the n-th shift redundancy circuit, andgenerating a second spare cell control signal; and a plurality ofinverters, each connected to a respective output terminal of thecorresponding shift redundancy circuit and connected to an outputterminal of the first and second spare cell control circuits, forinverting voltage levels of the output terminals and outputtingcorresponding final word line control signals.

In an exemplary embodiment, an n−1-th shift redundancy circuit of theshift redundancy circuits in the semiconductor memory device mayinclude: a first transmission switch for receiving an n-th shift wordline control signal in response to the third output signal of the n-thshift redundancy circuit and transmitting the n-th shift word linecontrol signal to a first node; a third transmission switch forreceiving an n−2-th word line control signal while being controlled bythe second output signal of the n−2-th shift redundancy circuit andtransmitting the received n−2-th word line control signal to the firstnode; a downward buffer chain for receiving a third output signal of then-th shift redundancy circuit and an output signal of the upper fuse,logically multiplying the received signals, and outputting a result ofthe logical multiplication operation as a third output signal of then−1-th shift redundancy circuit; an upward buffer chain for receiving asecond output signal of the n−2-th shift redundancy circuit and anoutput signal of the lower fuse, logically multiplying the receivedsignals and outputting a result of the logical multiplication operationas a second output signal of the n−1-th shift redundancy circuit; afirst NAND circuit for receiving the third output signal of the n−1-thshift redundancy circuit and the second output signal of the n−1-thshift redundancy circuit, NANDing the received signals and transmittinga result of the NAND operation to a control node of a secondtransmission switch; and the second transmission switch for receiving ann−1-th word line control signal while being controlled by an output ofthe first NAND circuit and transmitting the received n−1-th word linecontrol signal to the first node.

In an exemplary embodiment, an n−1-th upper fuse cut-out detectingcircuit of the plurality of fuse cut-out detecting circuits in thesemiconductor memory device may include: an eighth PMOS transistorhaving a gate electrode to which an output signal of an n−1-th upperfuse is applied, a source electrode to which a power supply voltage isapplied and a drain electrode from which an output signal of thedetecting circuit is generated; a sixth NMOS transistor having a drainelectrode connected to a gate electrode of the eighth PMOS transistorand a source electrode connected to a ground voltage, wherein the sixthNMOS transistor performs switching operations in response to a resetsignal, and a latch circuit connected between the gate electrode of theeighth PMOS transistor and the ground voltage for keeping a voltagelevel of the gate electrode of the eighth PMOS transistor with logic“low” when the output signal of the n−1-th upper fuse has a logic “low”level.

In an exemplary embodiment, an n−1-th lower fuse cut-out detectingcircuit of the lower fuse cut-out detecting circuits in thesemiconductor memory device may include: a ninth PMOS transistor havinga gate electrode to which an output signal of an n−1-th lower fuse isapplied, a source electrode to which a power supply voltage is applied,and a drain electrode from which an output signal of the detectingcircuit is generated, an eighth NMOS transistor having a drain electrodeconnected to the gate electrode of the ninth PMOS transistor and asource electrode to which a ground voltage is applied, wherein theeighth NMOS transistor performs switching operations in response to areset signal, and a latch circuit connected between the gate electrodeof the ninth PMOS transistor and the ground voltage for keeping avoltage level of the gate electrode of the ninth PMOS transistor withlogic “low” when the output signal of the n−1-th lower fuse has a logic“low” level.

In an exemplary embodiment, the first spare cell control circuit in thesemiconductor memory device may include: a first transmission gate beingcomprised of a first PMOS transistor and a first NMOS transistor, forreceiving the first word line control signal by being controlled by thethird output signal of the first shift redundancy circuit, the thirdoutput signal being input to a gate electrode of the first PMOStransistor, and transmitting the first word line control signal to anoutput node of the first spare cell control circuit, a first inverterfor inverting a voltage level of the gate electrode of the first PMOStransistor and applying the inverted voltage level to a gate electrodeof the first NMOS transistor; and a third PMOS transistor connectedbetween the output node of the first spare cell control circuit and apower supply voltage, and having a gate electrode connected to the gateelectrode of the first NMOS transistor.

In an exemplary embodiment, the second spare cell control circuit in thesemiconductor memory device may include: a second transmission gatebeing comprised of a second PMOS transistor and a second NMOStransistor, for receiving the n-th word line control signal while beingcontrolled by the second output signal of the n-th shift redundancycircuit, wherein the second output signal is input to a gate electrodeof the second PMOS transistor, and transmitting the received n-th wordline control signal to an output node of the second spare cell controlcircuit; a second inverter for inverting a voltage level of the gateelectrode of the second PMOS transistor and transmitting the invertedvoltage level to a gate electrode of the second NMOS transistor; and afourth PMOS transistor connected between the output node of the secondspare cell control circuit and a power supply voltage, and having a gateelectrode connected to the gate electrode of the second NMOS transistor.

Another exemplary embodiment of the present invention provides asemiconductor memory device with two spare memory cell rows and at leastone defective memory cell row, wherein when the semiconductor memorydevice has one defective memory cell row, a first spare memory cell rowof the two spare memory cell rows is positioned at a lowermost portionof a memory cell array and a second spare memory cell row is positionedat an uppermost portion of the memory cell array, and wherein word linecontrol signals are shifted upward or downward to control correspondingprevious or subsequent word lines by cutting out an upper fuse or alower fuse corresponding to the defective memory cell row.

In an exemplary embodiment, when the semiconductor memory device has twodefective memory cell rows including a first defective memory cell rowand a second defective memory cell row, the first defective memory cellrow positioned at a lower portion of the memory cell array is replacedwith the first spare memory cell row by cutting out the upper fusecorresponding to the first defective memory cell row, and the seconddefective memory cell row position at an upper portion of the memorycell array is replaced with the second spare memory cell row by cuttingout the lower fuse corresponding to the second defective memory cellrow.

Another exemplary embodiment of the present invention provides asemiconductor memory device, comprising: a memory cell array with atleast two spare memory cell rows; wherein when the semiconductor memorydevice has two spare memory cell rows, a spare memory cell row of thetwo spare memory cell rows is positioned at a lowermost portion of thememory cell array in the semiconductor memory device and the other ofthe two spare memory cell rows is positioned at an uppermost portion ofthe memory cell array, when semiconductor memory device has three sparememory cell rows, a spare memory cell row of the three spare memory cellrows is positioned at the lowermost portion of the memory cell array inthe semiconductor memory device, another of the three spare memory cellrows is positioned at the uppermost portion of the memory cell array,and a third of the three spare memory cell rows is positioned in amiddle portion of the memory cell array, and when the semiconductormemory device has four spare memory cell rows, a spare memory cell rowof the four spare memory cell rows is positioned at the lowermostportion of the memory cell array in the semiconductor memory device,another of the four spare memory cell rows is positioned at theuppermost portion of the memory cell array, and the other two of thefour spare memory cell rows are adjacent to each other and positioned inthe middle portion of the memory cell array.

Another exemplary embodiment of the present invention provides asemiconductor memory device, comprising: a memory cell array with N(where N is an integer >1) spare memory cell rows; wherein a first sparememory cell row of the N spare memory cell rows is positioned at alowermost portion of the memory cell array in the semiconductor memorydevice, a second of the N spare memory cell rows is positioned at anuppermost portion of the memory cell array, and any remaining sparememory cell rows of the N spare memory cell rows are positioned in amiddle portion of the memory cell array; wherein if N defective memorycell rows in the memory cell array divide the memory cell array into N+1memory cell array blocks, all N defective memory cell rows can berepaired as long as no more than N−1 defective memory cell rows occur inthe same memory cell array block.

Another exemplary embodiment of the present invention provides a methodof repairing N (where N is an integer >1) memory cell rows in a memorycell array, comprising: providing N spare memory cell rows in the memorycell array, arranged such that a first spare memory cell row of the Nspare memory cell rows is positioned at the lowermost portion of thememory cell array in the semiconductor memory device, a second of the Nspare memory cell rows is positioned at an uppermost portion of thememory cell array, and any remaining spare memory cell rows of the Nspare memory cell rows are positioned in a middle portion of the memorycell array; wherein the N defective memory cell rows in the memory cellarray divide the memory cell array into N+1 memory cell array blocks;and repairing all N defective memory cell rows as long as no more thanN−1 defective memory cell rows occur in the same memory cell arrayblock.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be more clearlyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a schematic block diagram of a conventional semiconductormemory device;

FIG. 2 is a schematic block diagram of a semiconductor memory device inaccordance with an exemplary embodiment of the present invention;

FIG. 3 is an exemplary circuit diagram of a shift redundancy circuitshown in FIG. 2;

FIG. 4A and FIG. 4B are exemplary circuit diagrams of a fuse cut-outdetecting circuit shown in FIG. 2;

FIGS. 5A to 5C are exemplary layouts of semiconductor memory devices inaccordance with exemplary embodiments of the present invention, whereinthe semiconductor memory device has two spare memory cell rows; and

FIGS. 6A to 6C are exemplary layouts of semiconductor memory devices inaccordance with exemplary embodiments of the present invention, whereinthe semiconductor memory devices have different numbers of spare memorycell rows.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 2 is a schematic block diagram of a semiconductor memory device inaccordance with an exemplary embodiment of the present invention.Referring to FIG. 2, a semiconductor memory device in accordance with anexemplary embodiment of the present invention includes a row decoder 10,upper fuses FAU1 to FAUn, lower fuses FAD1 to FADn, shift redundancycircuits SF1 to SFn, upper fuse cut-out detecting circuits FCU1 to FCUn,lower fuse cut-out detecting circuits FCD1 to FCDn, spare cell controlcircuits SPC1, SPC2, and inverters INV3 to INV8.

Each of the fuses FAU1 to FAUn, FAD1 to FADn has an end connected to apower supply voltage Vcc and the opposite end connected to thecorresponding shift redundancy circuits SF1 to SFn and to thecorresponding fuse cut-out detecting circuits FCU1 to FCUn.

An n−1-th shift redundancy circuit SFn−1 receives an n−2-th word linecontrol signal WAn−2, an n−1-th word line control signal WAn−1, an n-thword line control signal WAn, an output signal FSUn−1 of an n−1-th upperfuse FAUn−1, an output signal FSDn−1 of an n−1-th lower fuse FADn−1, athird output signal DSOn of an n-th shift redundancy circuit SFn, asecond output signal USOn−2 of an n−2-th shift redundancy circuit SFn−2.Further, an n−1-th shift redundancy circuit SFn−1 outputs a first outputsignal WBn−1, a second output signal USOn−1, and a third output signalDSOn−1 thereof.

The upper fuse cut-out detecting circuit FCUn−1 receives an outputsignal FSUn−1 of the upper fuse FAUn−1 and a reset signal RESET, outputsan output signal DSUn−1 and transmits the output signal DSUn−1 to a nodeNn−1.

The lower fuse cut-out detecting circuit FCDn−1 receives an outputsignal FSDn−1 of the lower fuse FADn−1 and a reset signal RESET, outputsan output signal DSDn−1 and transmits the output signal DSDn−1 to thenode Nn−1.

A voltage level of the node Nn−1 is inverted by the inverter INV5 andthe inverted voltage level serves as an n−1-th final word line controlsignal WCn−1.

The first spare cell control circuit SPC1 receives a first word linecontrol signal WA1 and a third output signal DSO1 of the first shiftredundancy circuit SF1, and generates an output signal WSB 1. The outputsignal WSB 1 of the first spare cell control circuit SPC1 is inverted inits voltage level by the inverter INV8, and the inverted signal servesas a first spare cell control signal WSC1. The first spare cell controlcircuit SPC1 includes a first transmission gate including a first PMOStransistor PM1 and a first NMOS transistor NM1. The first transmissiongate receives a first word line control signal WA1 while beingcontrolled by the third output signal DSO1 of the first shift redundancycircuit SF1, the third output signal DSO1 being inputted to a gateelectrode of the first PMOS transistor PM1, and transmits the first wordline control signal WA1 to an output node of the first spare cellcontrol circuit SPC1. The first spare cell control circuit SPC1 furtherincludes a first inverter INV1 for inverting a voltage level of theinput signal of the gate electrode of the first PMOS transistor PM1 andapplying the inverted voltage level to a gate electrode of the firstNMOS transistor NM1. The first spare cell control circuit SPC1 furtherincludes a third PMOS transistor PM3 connected between the output nodeof the first spare cell control circuit SPC1 and a power supply voltageline. The third PMOS transistor PM3 has a gate electrode connected tothe gate electrode of the first NMOS transistor NM1.

The second spare cell control circuit SPC2 receives the n-th word linecontrol signal WAn and a second output signal USOn of the n-th shiftredundancy circuit SFn, and generates an output signal WSB2. The outputsignal WSB2 of the second spare cell control circuit SPC2 is inverted bythe inverter INV3 and the inverted output signal of the second sparecell control circuit SPC2 serves as a second spare cell control signalWSC2. The second spare cell control circuit SPC2 includes a secondtransmission gate including a second PMOS transistor PM2 and a secondNMOS transistor NM2. The second transmission gate receives the n-th wordline control signal WAn in response to the second output signal USOn ofthe n-th shift redundancy circuit SFn, which is input to a gateelectrode of the second PMOS transistor PM2, and transmits the n-th wordline control signal WAn to an output node of the second spare cellcontrol circuit SPC2. The second spare cell control circuit SPC2 furtherincludes a second inverter INV2 for inverting a voltage level of theinput signal of the gate electrode of the second PMOS transistor PM2 andapplying the inverted voltage level to a gate electrode of the secondNMOS transistor NM2. The second spare cell control circuit SPC2 stillfurther includes a fourth PMOS transistor PM4 which is connected betweenthe output node of the second spare cell control circuit SPC2 and apower supply voltage, and has a gate electrode connected to the gateelectrode of the second NMOS transistor NM2.

The shift redundancy circuits SF1 and SFn which may be between the firstand second spare cell control circuits SPC1, SPC2, respectively, receivea power supply voltage Vcc and a ground voltage Vss as inputs.

FIG. 3 illustrates a shift redundancy circuit shown in FIG. 2,particularly illustrates a detailed circuitry of the n−1-th shiftredundancy circuit SFn−1.

Referring to FIG. 3, the shift redundancy circuit SFn−1 includes a firsttransmission switch T1 for receiving the n-th word line control singalWAn while being controlled by the third output signal DSOn of the n-thshift redundancy circuit SFn and transmitting the received signal to thenode Nn−1, a third transmission switch T3 for receiving the n−2-th wordline control signal WAn−2 while being controlled by a second outputsignal USOn−2 of the n−2-th shift redundancy circuit SFn−2 andtransmitting the received signal to the node Nn−1, and a downward bufferchain DBC for receiving the third output signal DSOn of the n-th shiftredundancy circuit SFn and the output signal FSUn−1 of the upper fuseFAUn−1, logically multiplying the received signals and generating athird output signal DSOn−1 of the n−1-th shift redundancy circuit SFn−1as a result of the logical multiplication operation. The shiftredundancy circuit SFn−1 further includes an upward buffer chain UBC forreceiving the second output signal USOn−2 of the n−2-th shift redundancycircuit SFn−2 and the output signal FSDn−1 of the lower fuse FADn−1,logically multiplying the received signals and generating a secondoutput signal USOn−1 of the n−1-th shift redundancy circuit SFn−1. Theshift redundancy circuit SFn−1 still further includes a NAND circuitNAND3 for receiving the third output signal DSOn−1 of the n−1-th shiftredundancy circuit SFn−1 and the second output signal USOn−1 of then−1-th shift redundancy circuit SFn−1, performing the NAND operationusing the received signals, generating an output signal as a result ofthe NAND operation and transmitting its output signal to a node NN2. Theshift redundancy circuit SFn−1 further includes a second transmissionswitch T2 for receiving the n−1-th word line control signal WAn−1 inresponse to the output signal of the NAND circuit NAND3 and transmittingthe received word line control signal WAn−1 to the node Nn−1.

The first transmission switch T1 includes a transmission gate TG3further including a PMOS transistor PM5 and an NMOS transistor NM3, andan inverter INV9 which is connected between a gate electrode of the PMOStransistor PM5 and a gate electrode of the NMOS transistor NM3, invertsthe third output signal DSOn of the n-th shift redundancy circuit SFn,and transmits the inverted third output signal to the gate electrode ofthe NMOS transistor NM3. The second and third transmission switches T2,T3 have the same configurations as the first transmission switch T1.

The downward buffer chain DBC includes a NAND circuit NAND1 forreceiving the third output signal DSOn of the n-th shift redundancycircuit SFn and the output signal FSUn−1 of the n−1-th upper fuse FAUn−1and logically multiplying the received signals, and an inverter INV12for inverting an output of the NAND circuit NAND1.

The upward buffer chain UBC includes a NAND circuit NAND2 for receivingthe second output signal USOn−2 of the n−2-th shift redundancy circuitSFn−2 and the output signal FSDn−1 of the n−1-th lower fuse FADn−1 andlogically multiplying the received signals, and an inverter INV13 forinverting the output of the NAND circuit NAND2.

FIGS. 4A and 4B illustrate exemplary circuits of an upper fuse cut-outdetecting circuit FCUn−1 and a lower fuse cut-out detecting circuitFCDn−1, respectively. The upper fuse cut-out detecting circuit FCUn−1includes a PMOS transistor PM8, an NMOS transistor NM6, an inverterINV14 and an NMOS transistor NM7. The PMOS transistor PM8 has a gateelectrode to which the output signal FSUn−1 of the upper fuse FAUn−1 isapplied, a source electrode to which a power supply voltage Vcc isapplied, and a drain electrode from which an output signal DSUn−1thereof is generated. The NMOS transistor NM6 has a drain electrodeconnected to the gate electrode of the PMOS transistor PM8, a sourceelectrode to which a ground voltage Vss is applied, and a gate electrodefor receiving a reset signal RESET. The inverter INV14 inverts theoutput signal FSUn−1 of the upper fuse FAUn−1 and outputs the invertedsignal of the output signal FSUn−1 of the upper fuse FAUn−1. The NMOStransistor NM7 has a drain electrode connected to the gate electrode ofthe PMOS transistor PM8, a source electrode to which a ground voltageVss is applied, and a gate electrode for receiving the output of theinverter INV14. The NMOS transistor NM7 and the inverter INV14 form alatch LATCH.

The lower fuse cut-out detecting circuit FCDn−1 includes a PMOStransistor PM9, an NMOS transistor NM8, an inverter INV15 and an NMOStransistor NM9. The PMOS transistor PM9 has a gate electrode to which anoutput signal FSDn−1 of a lower fuse FADn−1 is applied, a sourceelectrode to which a power supply voltage Vcc is applied, and a drainelectrode from which an output signal DSDn−1 thereof is generated. TheNMOS transistor NM8 has a drain electrode connected to the gateelectrode of the PMOS transistor PM9, a source electrode to which aground voltage Vss is applied, and a gate electrode for receiving areset signal RESET. The inverter INV15 inverts the output signal FSDn−1of the lower fuse FADn−1 and outputs an inverted output signal having anopposite logic level to the output signal FSDn−1 of the lower fuseFADn−1. The NMOS transistor NM9 has a drain electrode connected to thegate electrode of the PMOS transistor PM9, a source electrode to which aground voltage Vss is applied, and a gate electrode for receiving theoutput of the inverter INV15. The NMOS transistor NM9 and the inverterINV15 form a latch LATCH.

The operation of the semiconductor memory device in accordance with thepresent invention will be described below with reference to FIGS. 2 to4. For the sake of convenience of the explanation, the operation of ann−1-th shift redundancy circuit SFn−1 receiving an n−1-th word linecontrol signal WAn−1 as an input will be described.

A row decoder 10 decodes n-bit of row addresses and outputs word linecontrol signals WA1 to WAn. Final word line control signals WC1 to WCn,and two spare cell control signals WSC1, WSC2 control 8 memory cell rowsin a memory cell array (not shown). A reset signal RESET resets thefinal word line control signals WC1 to WCn through upper and lower fusecut-out detecting circuits FCU1 to FCUn, FCD 1 to FCDn before theoperation of the semiconductor memory device starts.

If there are no defective memory cells in the memory cell arraycontrolled by the final word line control signals WC1 to WCn and repairwork of the memory cells is not needed, the upper fuse FAUn−1 and thelower fuse FADn−1 are not cut out, so that their output signals FSUn−1and FSDn−1 have a logic “high” level. Accordingly, a second transmissionswitch T2 is turned on and a first and third transmission switches T1,T3 are turned off. In this state, the semiconductor memory deviceoperates as a normal semiconductor memory device with no shiftredundancy circuits. That is, word line control signals WA1 to WAnbecome the corresponding final word line control signals WC1 to WCn,respectively.

However, if there is a defective memory cell in a memory cell rowcontrolled by the n−1-th word line control signal WAn−1, the defectivememory cell may be repaired by cutting out either the upper fuse FAUn−1or the lower fuse FADn−1.

Assuming that only the upper fuse FAUn−1 is cut out, a second outputsignal USOn−2 of an n−2-th shift redundancy circuit SFn−2, a thirdoutput signal DSOn of an n-th shift redundancy circuit SFn and an outputsignal FSDn−1 of an n−1-th lower fuse FADn−1 have a logic “high” level.Since an output signal FSUn−1 of the upper fuse FAUn−1 has a logic “low”level, the third output signal DSOn−1 of the n−1-th shift redundancycircuit SFn−1 and the third output signal DSOn−1, an output of adownward buffer chain DBC, becomes a logic “low” level. Accordingly, anoutput of a NAND circuit NAND3 becomes a logic “high” level, and asecond transmission switch T2 is turned off. Since, the second outputsignal USOn−2 of the n−2-th shift redundancy circuit SFn−2 and the thirdoutput signal DSOn of the n-th shift redundancy circuit SFn have a logic“high” level, the first and the third transmission switches T1, T3 areturned off. Since the output signal FSUn−1 of the upper fuse FAUn−1 hasa logic “low” level, the PMOS transistor PM8 is turned on with referenceto FIG. 4A, and an output signal DSUn−1 of an upper fuse cut-outdetecting circuit FCUn−1 becomes a logic “high” level. This signal makesa logic state of a node Nn−1 high, so that the n−1-th final word linecontrol signal WCn−1 which is the output of the inverter INV5 becomeslogic “low” and the n−1-th word line is disabled. When only the n−1-thupper fuse FAUn−1 is cut out, all the outputs of the downward bufferchains DBC of the shift redundancy circuits SFn−1 to SF1 have a logic“low” level, and only the output of the downward buffer chain DBC of then-th shift redundancy circuit SFn has a logic “high” level. Further, allthe outputs of the upward buffer chains in all the shift redundancycircuits SF1 to SFn have a logic “high” level.

When only the n−1-th upper fuse FAUn−1 is cut out, the operation of then−2-th shift redundancy circuit SFn−2 will be described below.

Since, a logic “low” level of the third output signal DSOn−1 of then−1-th shift redundancy circuit SFn−1 is applied to the downward bufferchain DBC of the n−2-th shift redundancy circuit SFn−2, a secondtransmission switch T2 and a third transmission switch T3 of the n−2-thshift redundancy circuit SFn−2 are turned off. The n−2-th shiftredundancy circuit SFn−2 is different from the n−1-th shift redundancycircuit SFn−1 in that a logic “low” level of the third output signalDSOn−1 of the n−1-th shift redundancy circuit SFn−1 is input to thefirst transmission switch T1 of the n−2-th shift redundancy circuitSFn−2, so that the first transmission switch T1 of the n−2-th shiftredundancy circuit SFn−2 is turned on and an n−1-th word line controlsignal WAn−1 is transmitted to an output node Nn−2 (not shown) of then−2-th shift redundancy circuit SFn−2. Since the n−2-th upper fuseFAUn−2 (not shown) and the n−2-th lower fuse FADn−2 (not shown) are notcut out, the PMOS transistors PM8, PM9 of the upper fuse cut-outdetecting circuit FCUn−2 and the lower fuse cut-out detecting circuitFCDn−2 are turned off. Accordingly, the n−1-th word line control signalWAn−1 becomes the n−2-th final word line control signal WCn−2.

In the same manner as described above, the n−1-th final word linecontrol signal WCn−1 is disabled, and the n−2-th final word line controlsignal WCn−2 to the first final word line control signal WC1 are enabledby the n−1-th word line control signals WAn−1 to the second word linecontrol signal WA2. For the first spare cell control circuit SPC1, thetransmission switch TG1 is turned on by a logic “low” level of the thirdoutput signal DSO1 of the first shift redundancy circuit SF1, and thefirst word line control signal WA1 finally serves as a first spare cellcontrol signal WSC1, so that the memory cells connected to the firstspare cell control signal WSC1 may be used.

Assuming that only the n−1-th lower fuse FADn−1 is cut out, the secondoutput signal USOn−2 of the n−2-th shift redundancy circuit SFn−2, thethird output signal DSOn of the n-th shift redundancy circuit SFn, andthe output signal FSDn−1 of the n−1-th upper fuse FAUn−1 have a logic“high” level. Since the output signal FSDn−1 of the lower fuse FADn−1has a logic “low” level, an output signal of the upper buffer chain UBC,which is a second output signal USOn−1 of the n−1-th shift redundancycircuit SFn−1, becomes a logic “low” level. Accordingly, an output ofthe NAND circuit NAND3 becomes a logic “low” level, and the secondtransmission switch T2 is turned off. Since both of the second outputsignal USOn−2 of the n−2-th shift redundancy circuit SFn−2 and the thirdoutput signal DSOn of the n-th shift redundancy circuit SFn have a logic“high” level, the first and the third transmission switches T1, T3 areturned off. Since the output signal FSDn−1 of the lower fuse FADn−1 hasa logic “low” level, with reference to FIG. 4B, the PMOS transistor PM9is turned on and the output signal DSDn−1 of the lower fuse cut-outdetecting circuit FCDn−1 has a logic “high” level. This signal makes thenode Nn−1 a logic “high” level. Accordingly, the n−1-th final word linecontrol signal WCn−1 which is the output of the inverter INV5 becomes alogic “low” level and the n−1-th word line is disabled. In the case thatonly the n−1-th lower fuse FADn−1 is cut out, the outputs of the upperbuffer chains UBC of the shift redundancy circuits SFn−1, SFn have alogic “low” level, and the outputs of the upper buffer chains UBC of theshift redundancy circuits SFn−2 to SF1 have a logic “high” level.Further, for all the shift redundancy circuit SF1 to SFn, all theoutputs of the lower buffer chains have a logic “high” level.

When only the n−1-th upper fuse FAUn−1 is cut out, the operation of then-th shift redundancy circuit SFn will be described below.

Since a logic “low” level of the second output signal USOn−1 of then−1-th shift redundancy circuit is applied to the upper buffer chain UBCof the n-th shift redundancy circuit SFn, the second transmission switchT2 and the first transmission switch T1 of the n-th shift redundancycircuit SFn are turned off as those of the n−1-th shift redundancycircuit SFn−1. However, the n-th shift redundancy circuit SFn isdifferent from the n−1-th shift redundancy circuit in that a logic “low”level of the second output signal USOn−1 of the n−1-th shift redundancycircuit SFn−1 is applied to the third transmission switch T3, the thirdtransmission switch T3 of the n-th shift redundancy circuit SFn isturned on and the n−1-th word line control signal WAn−1 is transmittedto the output node Nn of the n-th shift redundancy circuit SFn. Sinceboth of the n-th upper fuse FAUn and the n-th lower fuse FADn are notcut out, the PMOS transistors PM8, PM9 of the upper fuse cut-outdetecting circuit FCUn and the lower fuse cut-out detecting circuit FCDnare turned off. Accordingly, the n−1-th word line control signal WAn−1becomes the n-th final word line control signal WCn.

In the same manner as described above, the n−1-th final word linecontrol signal WCn−1 is disabled and the n−1-th word line control signalWAn−1 becomes the n-th final word line control signal WCn. Further, then−2-th word line control signal WAn−2 to the first word line controlsignal WA1 become the n−2-th final word line control signal WCn−2 to thefirst final word line control signal WC1, respectively. For the secondspare cell control circuit SPC2, the transmission switch TG2 thereof isturned on by a logic “low” level of the second output signal USOn of then-th shift redundancy circuit SFn, and the n-th word line control signalWAn is used as the second spare cell control signal WSC2, so that thespare memory cell row connected to the spare cell control signal WSC2may be used.

When both of the n−1-th upper and lower fuses FAUn−1, FADn−1 are cutout, since downward shift operation of the word line control signals maybe performed by the downward buffer chains and upward shift operation ofthe word line control signals may be performed by the upward bufferchains, the semiconductor memory device may be repaired even when thesemiconductor memory device has two defective memory cell rows in thesame memory cell array block.

FIGS. 5A to 5C illustrate the repair operation of the semiconductormemory device in accordance with an exemplary embodiment of the presentinvention.

Referring to FIG. 5A, a memory cell array has a defective memory cellrow. At this time, word line control signals are shifted in onedirection, upward or downward, by cutting out the upper fuse or thelower fuse, as described above.

Referring to FIG. 5B, a memory cell array has two defective memory cellrows which are separate from each other. As shown, the memory cell arrayis divided into three memory cell array blocks MC3, MC4, MC5.

In a memory cell array block MC3, word line control signals are shifteddownward, and an upper fuse corresponding to the defective memory cellrow DMC2 is cut out. On the other hand, a memory cell array block MC4performs a normal operation and word line control signals are notshifted in the memory cell array block MC4. In a memory cell array blockMC5, word line control signals are shifted upward and a lower fusecorresponding to the defective memory row DMC3 is cut out.

Referring to FIG. 5C, a memory cell array has two defective memory cellrows which are adjacent to each other. At this time, the memory cellarray is divided into two memory cell array blocks MC6, MC7. The memorycell array block MC6 performs a downward shift operation, an upper fusecorresponding to the defective memory cell row DMC4 is cut out, and thememory cell array block MC7 performs an upward shift operation and alower fuse corresponding to the defective memory cell row DMC5 is cutout.

Accordingly, even if the defective memory cell rows are located at anyplace in a memory cell array, the defective memory cell rows can berepaired.

FIGS. 6A to 6C illustrate examples of the arrangements of spare memorycell rows in accordance with an exemplary embodiment of the presentinvention.

Referring to FIG. 6A, a semiconductor memory device has two spare memorycell rows SPR7, SPR8 in a memory cell array, and they are arranged atthe lowermost portion and the uppermost portion of a memory cell array,respectively. In this case, word line control signals are shifted eitherupward or downward, so that at least two defective memory cell rows canbe repaired.

Referring to FIG. 6B, a semiconductor memory device has three sparememory cell rows SPR9, SPR10, SPR11 which are located at the lowermost,middle and uppermost portions, respectively, of a memory cell array. Ifa semiconductor memory device with three spare memory cell rows has atotal three defective memory cell rows anywhere in the memory cellarray, and each memory cell array block in the memory cell array has twoor fewer defective rows, the semiconductor memory device can berepaired. For example, if a memory cell array block MC9 has twodefective memory cell rows and a memory cell array block MC10 has adefective memory cell row, one of the defective memory cell rows in theblock MC9 is repaired by using the spare memory cell row SPR9 by adownward shift operation of word line control signals and the otherdefective memory cell row in the block MC9 is repaired by using thespare memory cell row SPR10 by an upward shift operation of word linecontrol signals, and further the defective memory cell row in the memorycell array block MC10 is replaced with the spare memory cell row SPR11by an upward shift operation of word line control signals.

Referring to FIG. 6C, a semiconductor memory device has four sparememory cell rows SPR12, SPR13, SPR14 and SPR 15 in a memory cell array.Two spare rows SPR12, SPR15 are arranged in the lowermost and uppermostportions of the memory cell array, respectively, and the other twoSPR13, SPR14 are arranged in the middle portion of the memory cell arrayadjacent to each other. If the semiconductor memory device has a totalfour defective memory cell rows anywhere in the memory cell array, andeach memory cell array block in the memory cell array has two ordefective memory cell rows, the semiconductor memory device can berepaired. For example, if memory cell array blocks MC11, MC12 have twodefective memory cell rows therein, respectively, one of the defectivememory cell rows in the memory cell array block MC11 is replaced withthe spare memory cell row SPR12 by a downward shift operation of wordline control signals and the other in the block MC11 is replaced withthe spare memory cell row SPR13 by an upward shift operation of wordline control signals, and further one of the defective memory cell rowsin the memory cell array block MC12 is replaced with the spare memorycell row SPR14 by a downward operation of the word line control signalsand the other in the block MC12 is replaced with the spare memory cellrow SPR15 by an upward operation of the word line control signals.

As described above, exemplary embodiments of the present inventionprovide a semiconductor memory device allowing two or more defectivememory cell rows in the same memory cell array block to be repaired byusing spare memory cell rows. Further, the semiconductor memory devicesin accordance with exemplary embodiments of the present invention areadvantageous in that leakage current generated by fuse resistance isreduced and malfunction of the semiconductor memory device is reduced.

Although the exemplary embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A semiconductor memory device with two spare memory cell rows and atleast one defective memory cell row; wherein when the semiconductormemory device has one defective memory cell row, a first spare memorycell row of the two spare memory cell rows is positioned at a lowermostportion of a memory cell array and a second spare memory cell row ispositioned at an uppermost portion of the memory cell array, and whereinword line control signals are shifted upward or downward to controlcorresponding previous or subsequent word lines by cutting out an upperfuse or a lower fuse corresponding to the defective memory cell row. 2.The semiconductor memory device as set forth in claim 1, wherein whenthe semiconductor memory device has two defective memory cell rowsincluding a first defective memory cell row and a second defectivememory cell row, the first defective memory cell row positioned at alower portion of the memory cell array being replaced with the firstspare memory cell row by cutting out the upper fuse corresponding to thefirst defective memory cell row, and the second defective memory cellrow position at an upper portion of the memory cell array being replacedwith the second spare memory cell row by cutting out the lower fusecorresponding to the second defective memory cell row.
 3. Asemiconductor memory device, comprising: a memory cell array with atleast two spare memory cell rows; wherein when the semiconductor memorydevice has two spare memory cell rows, a spare memory cell row of thetwo spare memory cell rows is positioned at a lowermost portion of thememory cell array in the semiconductor memory device and the other ofthe two spare memory cell rows is positioned at an uppermost portion ofthe memory cell array, when semiconductor memory device has three sparememory cell rows, a spare memory cell row of the three spare memory cellrows is positioned at the lowermost portion of the memory cell array inthe semiconductor memory device, another of the three spare memory cellrows is positioned at the uppermost portion of the memory cell array,and a third of the three spare memory cell rows is positioned in amiddle portion of the memory cell array, and when the semiconductormemory device has four spare memory cell rows, a spare memory cell rowof the four spare memory cell rows is positioned at the lowermostportion of the memory cell array in the semiconductor memory device,another of the four spare memory cell rows is positioned at theuppermost portion of the memory cell array, and the other two of thefour spare memory cell rows are adjacent to each other and positioned inthe middle portion of the memory cell array.
 4. A semiconductor memorydevice, comprising: a memory cell array with N (where N is aninteger >1) spare memory cell rows; wherein a first spare memory cellrow of the N spare memory cell rows is positioned at a lowermost portionof the memory cell array in the semiconductor memory device, a second ofthe N spare memory cell rows is positioned at an uppermost portion ofthe memory cell array, and any remaining spare memory cell rows of the Nspare memory cell rows are positioned in a middle portion of the memorycell array; wherein if N defective memory cell rows in the memory cellarray divide the memory cell array into N+1 memory cell array blocks,all N defective memory cell rows can be repaired as long as no more thanN−1 defective memory cell rows occur in the same memory cell arrayblock.
 5. A method of repairing memory cell rows in a memory cell array,comprising: providing N spare memory cell rows in the memory cell array,arranged such that a first spare memory cell row of the N spare memorycell rows is positioned at the lowermost portion of the memory cellarray in the semiconductor memory device, a second of the N spare memorycell rows is positioned at an uppermost portion of the memory cellarray, and any remaining spare memory cell rows of the N spare memorycell rows are positioned in a middle portion of the memory cell array;wherein the N defective memory cell rows in the memory cell array dividethe memory cell array into N+1 memory cell array blocks; and repairingall N defective memory cell rows as long as no more than N−1 defectivememory cell rows occur in the same memory cell array block.
 6. Asemiconductor memory device with at least two spare memory cell rows andat least one defective memory cell row; wherein each of the at least twospare memory cell rows is positioned at one of a lowermost portion of amemory cell array, an uppermost portion of the memory cell array, and amiddle portion of the memory cell array, and wherein word line controlsignals for controlling corresponding word lines connected to memorycells in the memory cell array are shifted upward or downward, therebyreplacing each of the at least one defective memory cell row with atleast one of the at least two spare memory cell rows.